The invention concerns a disk valve for a fluid under pressure.
A disk valve is known from DE-A-4135858 which comprises a) a housing with an inlet and an outlet; b) one fixed plate mounted inside the housing, the plate cam having one port for the fluid; c) a second plate cam, also mounted inside the housing, and able to rotate about an axis, this cam resting on the fixed plate cam, and having a second port for the fluid which is not concentric to the axis and which is infinitely variable between an open position in alignment with the first port and a misaligned closed position; and d) a pressure relief surface concentric to the rotating plate cam, which is in contact with the outlet pressure of the fluid, in the closed position at least.
In the known valve, the pressure relief area is formed by the front face of a piston which is moulded on to a guide disk connected to the rotating plate cam. When this known valve is in its closed position, a tilting moment acting on the plate disc develops, which is due to the fact that the pressure relief force caused by the piston is, in fact, concentric to the rotating plate cam which, in contrast, is eccentric to the force of pressure applied to the rotating plate cam in the area around the port in the fixed plate cam. The latter is therefore due to the fact that a sealing band is formed which closely encircles the port of the fixed plate cam--also presumably under the influence of a slight elastic deformation of the rotating plate cam which is "hollow" at this point. The rotating plate cam is therefore largely pressure-compensated outside the area above the port of the fixed plate cam. At very high pressures, the tilting moment caused by the foregoing action can lead to leakage from the disk valve when it is in the closed position. To avoid this with the known valve, the size of the pressure relief area formed on the piston must not be too large. The concept of relieving the pressure from the rotating plate cam can therefore not be carried quite so far as would actually be possible and even desirable if there was no tilting moment phenomenon present.